1. Field of the Invention
The present invention generally relates to an isolator mount. Specifically, the invention is an isolation mechanism having energy dissipating materials integrated therein so as to impede both shocks and vibrations.
2. Related Arts
Naval ships employ a wide variety of isolator mounts to impede acoustic transmissions and to protect sensitive equipment from shocks and vibrations. Presently, isolator mounts are specifically designed for a limited range of shocks and vibrations. As such, a variety of mounts are required to satisfy a wide range of mechanical load conditions.
Energy dissipation mechanisms employed within presently known devices quickly degrade with use thereby requiring frequent replacement. For example, passive mounts comprised of rubber and metal rapidly lose their damping capacity. Consequently, isolator mounts are often used well beyond their effective lifetime thereby compromising the integrity and performance of shipboard systems.
Active mounts with integrated electronics increase the range of shocks and vibrations effectively isolated. However, active mounts are generally less durable and more sensitive to environmental conditions. For example, wires externally attached to such devices are susceptible to breakage. Furthermore, electronics within such devices are susceptible to the very shocks and vibrations dissipated and likewise damaged by saltwater, ozone, and oil contaminants.
Low-frequency shocks, typically from 3 to 10 Hz, and vibrations, typically from 5 to 30 Hz, exclude many passive and active damping devices. For example, the effectiveness of viscoelastic damping increases with frequency and of limited utility at low frequencies. Passive damping by piezoelectric or electrostrictive devices, also referred to as direct effect damping devices, is not particularly useful at low bandwidths since damping is dependent upon hysteresis loops and elastic-mechanical-to-electrical energy coupling. Coupling coefficients are generally poor and total loss is insignificant at the lower dynamic range.
Piezopolymers are better direct coupling materials than piezoceramics and electrostrictors, therefore applicable to piezo-passive damping devices. In a passive-mode device, a generalized matched impedance circuit is coupled to active ferroelectric materials so as to transfer elastic energy to heat. In a semi-active mode, the circuit is variably tunable. However, strength and stiffness characteristics preclude the use of ferroelectric polymers, examples including PVDF and urethane, as active devices.
What is required is an isolator mount possessing both soft damping for small disturbance excitations and stiffness to mitigate large shocks.
What is required is an isolator mount having a high level of damping effective against shocks and vibrations, yet sufficiently stiff otherwise.
What is required is an isolator mount that functions over a wide range of temperature and load conditions.